let a = new Number()
console.log(a)
console.log(typeof a)
a = a + 1
// console.log(a = a + 1)
console.log(a)
console.log(typeof a)

let b = new Boolean()
console.log(b)
console.log(typeof b)
b = !b
console.log(typeof b)

let c = new String()
console.log(c)
console.log(typeof c)

c = c +'21312312'
console.log(c)
console.log(typeof c)

if({}){
  console.log('{}为true')
}

